package com.doyutu.seed.config.shiro;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.shiro.web.filter.authc.BasicHttpAuthenticationFilter;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMethod;

/**
 * @author DoyuTu
 * @version 0.0.1 spring-boot-project-seed
 */
public class JWTFilter extends BasicHttpAuthenticationFilter {

  /**
   * 判断用户是否想要登入。
   * 检测header里面是否包含Authorization字段即可
   */
  @Override
  protected boolean isLoginAttempt(ServletRequest request, ServletResponse response) {
    HttpServletRequest req = (HttpServletRequest) request;
    String authorization = req.getHeader("Authorization");
    return authorization != null;
  }

  /**
   *
   */
  @Override
  protected boolean executeLogin(ServletRequest request, ServletResponse response) {
    HttpServletRequest httpServletRequest = (HttpServletRequest) request;
    String authorization = httpServletRequest.getHeader("Authorization");

    JWTToken token = new JWTToken(authorization);
    // 提交给realm进行登入，如果错误他会抛出异常并被捕获
    getSubject(request, response).login(token);
    // 如果没有抛出异常则代表登入成功，返回true
    return true;
  }

  /**
   * 这里我们详细说明下为什么最终返回的都是true，即允许访问
   * 例如我们提供一个地址 GET /article
   * 登入用户和游客看到的内容是不同的
   * 如果在这里返回了false，请求会被直接拦截，用户看不到任何东西
   * 所以我们在这里返回true，Controller中可以通过 subject.isAuthenticated() 来判断用户是否登入
   * 如果有些资源只有登入用户才能访问，我们只需要在方法上面加上 @RequiresAuthentication 注解即可
   * 但是这样做有一个缺点，就是不能够对GET,POST等请求进行分别过滤鉴权(因为我们重写了官方的方法)，但实际上对应用影响不大
   */
  @Override
  protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) {
    if (isLoginAttempt(request, response)) {
      try {
        executeLogin(request, response);
      } catch (Exception e) {
        response401(request, response);
      }
    }
    return true;
  }

  /**
   * 对跨域提供支持
   */
  @Override
  protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {
    HttpServletRequest httpServletRequest = (HttpServletRequest) request;
    HttpServletResponse httpServletResponse = (HttpServletResponse) response;
    httpServletResponse.setHeader("Access-control-Allow-Origin", httpServletRequest.getHeader("Origin"));
    httpServletResponse.setHeader("Access-Control-Allow-Methods", "GET,POST,OPTIONS,PUT,DELETE");
    httpServletResponse.setHeader("Access-Control-Allow-Headers", httpServletRequest.getHeader("Access-Control-Request-Headers"));
    // 跨域时会首先发送一个option请求，这里我们给option请求直接返回正常状态
    if (httpServletRequest.getMethod().equals(RequestMethod.OPTIONS.name())) {
      httpServletResponse.setStatus(HttpStatus.OK.value());
      return false;
    }
    return super.preHandle(request, response);
  }

  /**
   * 将非法请求跳转到 /401
   */
  private void response401(ServletRequest req, ServletResponse resp) {
    try {
      req.getRequestDispatcher("/401").forward(req, resp);
    } catch (IOException | ServletException e) {
      e.printStackTrace();
    }
  }
}
